Disk caching of UIWebView resources on iOS 4.2

[kemenaran]

Starting from iOS 4.2, all NSCachedURLResponse coming from an UIWebView have a storagePolicy set to NSURLCacheStorageAllowedInMemoryOnly (instead of NSURLCacheStorageAllowed in the previous iOS versions).

Of course, as SDURLCache honors the storagePolicy, it won't cache any of the UIWebView response to the disk.

In order to fix this, I implemented an option that force SDURLCache to cache requests with NSURLCacheStorageAllowedInMemoryOnly. This option is enabled by default when running on iOS >= 4.2 (and disabled otherwise).

It may impact performances (as the InMemoryOnly policy is always ignored, even when legitimate). Maybe there is a better way to hook into the UIWebView NSURLConnection or NSURLProtocol to fix this?

[rs]

I merged your commit with some refactoring. I also activated the option regardless of the iOS version because:
1/ it may lead to bugs only reproducible on certain version of iOS
2/ I think only UIWebView use memory only storage policy

Thanks for your valuable contribution.